In a host-based mobility protocol, e.g., DSMIPv6, a user equipment (UE) (or mobile node) typically extends its Internet Protocol (IP) stack and implements IP mobility signaling as the UE moves and changes its point of attachment. For this reason, DSMIPv6 is often referred as a client MIP (CMIP). FIG. 1 illustrates a conventional network 100 including a user equipment (UE) 104, an access router (AR) 106, and a home agent (HA) 108. As shown in FIG. 1, user equipment 104 is communicating via a home link 102 to a home network.
FIG. 2 illustrates a conventional attach procedure 200 during which user equipment 104 gains network connectivity to a home network via a home link. At step 202, user equipment 104 performs a layer 2 specific attach procedure with access router 106. At step 204, user equipment 104 performs a layer 3 specific procedure to configure an IP address on an interface of user equipment 104. User equipment 104 also performs a home link detection procedure and detects that user equipment 104 is at home and therefore, the IP address previously obtained is a home address associated with user equipment 104. At step 206, user equipment 104 can send and receive data traffic from a correspondent node (CN) 110 via the home address. In general, a correspondent node can be mobile or stationary.
FIG. 3 illustrates a conventional network 300 including a user equipment (UE) 306, an access router (AR) 308, and a home agent (HA) 310. As shown in FIG. 3, user equipment 306 is connected to a home network 304 via a visited network 302. FIG. 4 illustrates a conventional attach procedure 300 during which a user equipment 306 gains network connectivity to a home network 304 via a foreign link (visited network 302).
Referring to FIG. 4, at step 402, user equipment 306 performs a layer 2 specific attach procedure with access router 308. At step 404, user equipment 306 performs a layer 3 specific procedure to configure an IP address on an interface of user equipment 306. By performing a home link detection procedure, user equipment 306 detects that user equipment 306 is not at home and therefore, the IP address previously obtained is a care-of address (CoA). At step 406, user equipment 306 then starts a bootstrapping procedure to obtain an IP address of home agent 310, if not available, using either DHCP or DNS. At step 408, user equipment 306 runs an IKEv2 protocol with home agent 310 to establish an IPSec security association. User equipment 306 can also obtain a home address (HoA) and a home network prefix during this procedure. At step 410, user equipment 306 registers the binding between the care-of address and the home address in a Binding Update message with home agent 310. Upon receiving this Binding Update message, home agent 310 creates a binding between the care-of address and the home address in a Binding Cache entry. At step 412, a Binding Acknowledgement message, if requested, is sent back from home agent 310 to notify user equipment 306 of the status of the Binding Update procedure. At step 414, user equipment 306 gains network connectivity and can send or receive data traffic from a correspondent node (CN) 312 at the current point of attachment.
In order to enable mobility service, both a UE and a home agent needs to allocate resources and maintain states. For example, a home agent needs to create a Binding Cache entry (if the UE attaches to a foreign link), establish and maintain an IPSec SA (if the UE attaches to a foreign link) and allocate a home address for the UE. On the other hand, the UE needs to create a Binding Update List entry, and establish and maintain an IPSec SA for each home agent that the UE connects to. The HA may have to discontinue IP mobility service provided to the UE sometimes, for example when a prepaid account associated with the UE contains insufficient funds or due to administration reasons. In this case, a home agent should remove related states and withdraw allocated resources, and also allow the UE to do so gracefully. Such a procedure is referred to as a network-initiated detach procedure. On the other hand, it is possible that a UE may decide to stop using mobility service at certain point of time. In such a case, a UE needs to remove allocated resources and also inform a HA to do so. This procedure is referred to as a UE-initiated detach procedure.
As specified in RFC 3775, “Mobile Support in IPv6”, each Binding Cache entry is associated with a lifetime. Therefore, when an HA decides to detach a UE from a home network, the HA may reject the request of binding renewal from the UE. In this way, the UE cannot update its binding and thus the UE cannot continue using mobility services. However, one obvious drawback of this mechanism is that the HA has to wait until the binding expires before the HA can withdraw and re-use resources allocated for the UE. Another approach is that the HA implicitly detaches the UE from the network without notifying the UE. However, this approach is not user-friendly.
Draft-muhanna-mip6-binding-revocation-02, “Binding Revocation for IPv6 Mobility”, proposes an approach to enable an HA to immediately revoke a binding of a UE. However, the draft does not specify how to withdraw other resources, such as the IPSec SA and the home address, and only discloses removal of the binding between a care-of address and a home address of a UE. A home address is usually assigned by an HA to a UE dynamically during the procedure of establishing an IPSec SA. The IKEv2 protocol allows either the HA or the UE to initiate the procedure to delete a pre-established IPSec SA; however, the IKEv2 protocol does not provide any indication on why an IPSec security association needs to be deleted or whether the UE needs to detach from the home network.